On Thu, Aug 18, 2016 at 02:52:31PM +0800, Yuanhan Liu wrote:

On Tue, Jul 05, 2016 at 06:19:24PM +0530, Jerin Jacob wrote:

quoted

Split out SSE instruction based virtio simple Rx
implementation to a separate file

Signed-off-by: Jerin Jacob <redacted>

Hi,

I was about to apply this set. I then did some build test and found a
weird issue: it breaks the build with clang (ubuntu 16.04).

    drivers/net/virtio/virtio_rxtx_simple_sse.c:130:2: error: cast from 'const void *' to 'void *' drops const qualifier [-Werror,-Wcast-qual]
            _mm_prefetch((const void *)rused, _MM_HINT_T0);
            ^
    /usr/lib/llvm-3.8/bin/../lib/clang/3.8.0/include/xmmintrin.h:684:58: note: expanded from macro '_mm_prefetch'
    #define _mm_prefetch(a, sel) (__builtin_prefetch((void *)(a), 0, (sel)))
                                                         ^
    1 error generated.

Weird enough I don't see this issue before this commit: the error
line is exactly the same before and after this commit.

Yes, I looked at the pre processed output as well, it comes as same before and
after this commit.

Another note is that _mm_prefetch() is actually with different prototype
for gcc and clang. For gcc, we have:

    _mm_prefetch (const void *__P, enum _mm_hint __I)

Any thoughts?

How about replacing "_mm_prefetch((const void *)rused, _MM_HINT_T0)"
with "rte_prefetch0(rused)" to have same prototype and fix the issue
with clang?

	--yliu